Background: Increasing interest has focused on the development of new assays more specific for APS and application of multiple combinations of anti-phospholipid antibodies (aPLs). This study explored the thrombotic risk of non-criteria aPLs measured by a new line immunoassay (LIA) and the benefit of additional non-criteria aPLs results to the APS diagnosis.
Methods: LIA were performed to detect 9 aPLs in 180 patients requested for lupus anticoagulant (LA) measurement. Antibodies against anti-cardiolipin (CL), β2 glycoprotein I (GPI), and β2GPI domain I were measured by ELISA.
Results: The agreement percentages for IgG/IgM anti-CL and anti-β2GPI between ELISA and LIA (anti-CL 68.2% and 82.6%; anti-β2GPI 71.7% and 93.2%, respectively). Among 9 aPLs measured by LIA, single presence IgG of anti-phosphatidylserine (odds ratio (OR) 16.477) and anti-phosphatidic acid (OR 9.625) predicted higher thrombotic risk than anti-β2GPI (OR 5.538). Other aPLs measured by LIA (anti-prothrombin, anti-annexin V, anti-phosphatidylinositol, phosphatidylethanolamine, and anti-phosphatidylglycerol) did not show any significant thrombotic risk. Addition of the 2 non-criteria aPLs (anti-phosphatidylserine and anti-phosphatidic acid) to the established APS criteria increased the diagnostic specificity and accuracy for thrombosis. The positive rates of anti-β2GPI and anti-phosphatidylserine measured by LIA were quite high in patients with positive anti-β2GPI domain I.
Conclusions: The anti-phosphatidylserine and anti-phosphatidic acid among non-criteria aPLs have a high likeli-hood as new markers for thrombotic prediction.